Traffic-control system for radio broadcast distribution



1,695,176 E. E. CLEMENT Filed April 10, 1925 8 Sheets-Sheet 1 Dec. 11, 1928.

TRAFFIC CONTROL SYSTEM FOR RADIO BROADCAST DISTRIBUTION Dec 11, 1928.

E. E. CLEMENT TAFFIC CONTROL.l SYSTEM FOR RADIO ROADGAST DISTRIBUTION Filed April l0, 1925 8 Sheets-Sheet 2 K NNN N TNW @NHT 6 3 7 .t 1u, Mw 5 .n Qwqw NIW 1TB U ,Be Ih RS I D T s A G D m5 TR Nw Emo, EA LRn CRT Op FA E Mm Ewl Si YF S L O R M O f` C C .M 8F wm 1T \Qvh llmmvbl 1 l Dec 1l, 1928.

E. CLEMENT TRAFFIC CONTROL SYSTEM FOR RADIO BROADCAST DISTRIBUTION Filed April 10, 1925 s Sheets-Sheet 4 Dec. il, 1928.

- E. E. CLEMENT TRAFFIC CONTROL SYSTEM FOR RADIO BROADCAST DISTRIBUTION Filed April lO, 1925 8 Sheets-Sheet 5 NQDN R www w NMUNI 92. N

MOM.

Dec ll, 1928.

E. E. CLEMENT TRAFFIC CONTROL SYSTEM FOR RADIO BROADCAST DISTRIBUTION Filed April lO, 1925 8 Sheets-Sheet 6 Dec. 11, 1928.

E. E. CLEMENT TRAFFIC 'CONTROL' SYSTEM FOR RADIO BROADCAST DISTRIBUTION Filed April lO, 1925 8 Sheets-Sheet '7 k Tb.

QH Q M. @Qu www @WN NWN www

Dec. ll, 1928. 1,695,176

E. E. CLEMENT TRAFFIC CONTROL SYSTEM FOR RADIO BROADCAST DISTRIBUTION 8 sheets-sheet e Filed Aprl 10, 1925 Ig/75C?. 6.

l Z bodying the inventiom lPtitenteti itil,

EDWARD E. CLEMENT, @"E TVASHINGTGN, DXSTRCT OF COLUMBA., ASSIGNR TO EDWARD?. CGLLADAY, 0F WASHINGTON, DISTRICT 0l? CGLUMBA.

TRAFFIG-CONTRGL SYSTEM FOR RADIQ BRUADCAST DESTRBUTION.

Application lled April 10,1925. Serial ".llo. 22,172.

tubes with a subscribers line and distributing radio broadcast matter therethrough to the subscriberssubstation. The system also provides means for affording the subscriber' a selection of different programs furnished by his associated central station or by other central stations of the system.

The invention is illustrated in the accompanying drawings in which:

Fig. 1 is a schematicdiagra-m of a semiautomatic telephone exchange system. em-

.Fig 2 shows a subscribers substation apparatus, line, and line terminal apparatus or primary control circuits and apparatus.

Fig. 3 shows a link circuit, for linking a' so calling line with an idle selector switch selection of a switching'mechanism affording access to groups of subscribers or broadcast programs.

Fig. 4 shows a connector trunk' and switch for selection of and connection with any one of a group of. subscribers line terminals.

Fig. 5 showsthe operators trunk with secondary selector switch and key set con- .rol.

6 shows the operators key. set and sending machine.'

Fig. 7 shows a subscribers party'line. Fig. 8 shows a broadcast service link circuit with line tube.

several sheets of drawings shoul be combined to show the entire system.v

As the combination of circuits and appa ratus constituting the general system here shown and its operation, are shown and described in detail in .Patent No. 1,230,996, granted tof me J une26, 1917, it will sutlce here to describe the general system inoutlne referring to the schematic diagram Fig.

1 for an understanding of the system of se- Ele tothe wipers of connector switches. The

Fg. 9 is a layout plan showin the lective switching forming an element of the present invention, a detailed descriptionv being given of what in the'present case is new over the disclosure of the patent above re' ferred to.

y-In Fig. 1, each element is marked with the title by which in general it will be designated throughout the case, and enough of the reference letters and numerals are shown for purposes of comparison and to gain a 05 general understanding of the relation of the various parts of the circuits shown in the other diagrams. It may be here stated that for convenience all calls for broadcast reception or .for telephone connections will be assumed to originate at the left hand end or station, and all connections to progress toward the right, the wanted or called subscriber being assumed as the right handsubscriber in every case. Of course, it will be understood that there is no such limitation in practice, but this assumption simplifies description and illustration. In this figure therefore three subscribers -stations are shown at the left hand end of the sheet, each go provided with 'a telephone set 'and a broadcast receiving set whose lines terminate on multiple cont-acts 'of three primaryl selector switches, each'of whichvhas a pivoted wi er or contact which can be swept over the me u contacts to connect with anyone of theml Each of .these wipers forms yone terminal of a selector trunk, the other terminalof which is a similar wiper in," the selector switch. The fixed contacts overwhich these wipers sweep in all the switches are usually referred to as bank contacts, and in mass as contact banks. Y i

From the bank contacts of the selector switches connector trunks are taken in multianks of these connector switches containV only line terminals, just the same as the rimary selectors. y At the right hand end of `ig. 1 two subscribers.- lines are shown, each with four subscribers stations connected to it in parallel.- These are arty lines, so

4shown for the` purpose of illustrating the principle of selective ringing. They need not all be party lines however, nor is it necessary that the subscribers shown on the right of, Fig. 1 should be different from those shown at the left. On the contrary, every subscriber.s line, in order to have complete service, must be connected in multiple to terminals inf both the primary selector switches and the connector switches, since it is through the former that the subscriber when calling reaches the central otlice, and it is through the connector switches thatthe centraloce .when calling reaches the subscriber.

Associated with each connector switch is an auxiliary or ringing selector switch. rlhe wiper ot this switch sweeps over contacts connected to several ringing' gener ators, each of which generates a particular distinctive character ot current. At the several stations on a party line thebellsare designed and adjusted so as to respond selecf tively and exclusively, each to its own particular kind of current only. At- `thelast stage in a connection, when the wanted-subscribers line has been picked out by the connector switch, and the ringing selector has been set so as to bring into service the proper generator, the wiper of that switch is then automatically connected through .the connector to the subscribers line to ring his bell. At all other times the ringing selector remains disconnected.v

The primary selector. switches are controlled by the subscribers in calling, through the medium of line relays at the central 'ofice which respond to the How of' current in the subscribers lines, and which when so energized guide and direct the rimary switch' wipers to their respective llne con tacts. A calling subscriber therefore gains access to the irst selector trunks in the central office by his own act alone. Inorder to continue the connection however, from the first selector trunk to the wanted subscriber, it is,necessary to actuate a selector switch, and a connector switch. The type qt switch employed in this system is electromagnetically driven by means of current impulses of predetermined number sent inpredetermined groups, which move vthe switch wipers step by step. over the bank contacts. These implulses are supplied, A and the switches are controlled, by operators, at the central office, who for that purpose are given access through secondary selector switches to the first selectory trunks, whereby they are enabled both to receive their orders from the calling subscribers,-by way of the primary selectors, and to sendimpulses to the first selector and succeeding switches, for the urpose of making the desired connection.

he secondary selector switches as will presently be seen, are initially res onsive toy the subscribers acts in calling. n fact, broadly speaking, their operation is the same as that of the primary selector, the fiow of current in a calling subscribers line and in the first selector ltrunk connected thereto causing a secondary selector switch wiper to lbe guided and'directed automatically to a conrecante Une of the signals associated with these. I

keys is ai calling lamp, which is lighted autornaticallywhen the key set becomes connected through the secondary switch to a rst selector trunk already connected to a subscribers line through a primary selector switch. Observing the signal, the operator asks the subscriber' for the number wanted, and proceeds to de ress the corresponding keys or buttons. he then presses a separate starting key, and groups ot impulses, corresponding'to the buttons depressed, will thereupon be transmitted through the keyset, through the secondary selector switch andv through the selector trunk to the selec tor switch, causing the following operations:

.i (l) rlhe selector switch is stepped around to the contact of a connectorv trunk leading to a. connector switch of the hundreds group corresponding to the first digit set up, (this vparticular connector containing terminals of the line wanted); (2 and 3) the connector switch is then stepped around in response to the second and third groups' of impulses to pick out the terminals of the line wanted; and (4) the associated ringing selector having been set in response to the operation of the impulses, the. wanted subscribers bell is automatically rung. j

ReferenceV has been made above to hundreds groups of circuits. This particular switching system is knownas a percentage trunking system. That is to say, the connection between any two lines iseffected by successive steps or successive acts of subdivision. Obviously therefore, access could be hadto any desired4 line by picking out a connectorof the hundreds group in which the line number occurred. That connector would then actuall contain terminals of the wanted lines.

switches is quite complicated because of the large number of -trunk'wires employed' to furnish the various combinations required between the switches, but the theory is quite simple, and is well enough illustrated in Fie. l. e

s soon as one ofthe subscribers at the left of Fig. 1 has become connected in the manner stated'with one of the subscribers at f course in practice the wiringvr between the different groups of negano the ri ht, it is unnecessary and in Jlact undesira le for the operator to remain longer in connection with them, and means are. provided for automatically cutting off' and restoring the secondary selector `switch as soon as this condition is brought about; Thererafterall the switches in use between the two subscribers are under their own control, and when they finally hang up their receivers the several switches vare automatically restored, the connection is broken, and all parts resume the positions of idleness diagraphically illustrated in Fig. 1.l

goingy that portions of the apparatus and circuits at the centraloiiice are common to allor a number of subscribers lines, whereby confusion might#A arise from simultaneous connection of more than oneline to the same trunk, inore than one trunk to the same line, more than one trunk to the same operator, or more than one operator to the sameftrunk. Special provision is made however, to prevent this. At the left of Fig.` 1, I have indi--v cated. what call a primary distributing switch and a. secondary distributing switch.

The first of these contains in its banks testy ingterminals of the primary switches or selector trunks. It is actuated'in response to the subscribers calls, and always acts to for connection with the calling line. There is only one distributing switch for all the primary selector, switches serving the same group of subscribers, hence only one switch' can' be started ata time, and this prevents more than one trunk being connected to the same line. In going to the line, the action of the primary switch is to test over its bank contacts until it reaches a contact which has had its lcondition changed, due to current flowing inthe calling line. If more than one line is, calling, the switch will stop atv thg. lirst one to vbe reached, and thereafter the distributing switch will start another primary selector to search for the second calling v line, whereby it isvimpossible for more than one line to get on the same trunk.

The 'secondary distributing switch performs the same functions with respect to the operators or secondary selector switches, and is actuatedv also in response to the subscribers7 calls, so as to-'start only one secondary selectorswitch at a time for any onek groupof trunks, Y

The foregoingis an outline description of the' apparatus and operations involvedin the establishment of a telephone connection between two subscribers. For establishing a broadcast service connection with ai subscriberthesamecamaratus and operation is involved except that-for this purpose the special broadcast service 'connector trunks are provided each containing an'amplifying' tube or tubes and. arranged to form a group` which is reached only and always through a special group of call numbers for example,

nthe tenth group. 1 The connector switches of thesebroadcast service trunksl are the same as those of the telephone service connector trunkslexcept that theii, bank'contacts form multiple taps ifrom a set of broadcast or program busses and trunks.

' Thus a subscriber desiri broadcast service simply calls for a 'num r in the tenth group representing the number of the program bus or trunk with lwhich he desires connection.v Being in the tenth group, ,the It will-be noted after reading the tore-- connection is lmade through a broadcast A service connector trunk containing an ampli- The, switching system or. telephone ex change system hereinishown, excepting those `portions in the special group (tenth group) assigned to broadcast distribution, is the same as that shownf1and 'describedin the patentl abovej referredto and to which refer` ence is to be had for adetailed showing and description of the switches'- erein shown diagrainmatically.U Itsuices hereto point .out that the selector and connector switches select and start up an idle switch and trunk are of the two motion type in which the movable contact wipers are arranged to have first a rotary motion tobring them in line vertical stepping magnets and a release magnet, the general function and operation of .which elements are well understood by those skilled in the art. As the apparatus and operation involved 1n the establishment of a connection for broadcast service is' the same as that` for-- a straight telephone connection except :for the substitution for a telephone connector trunk'of a broadcast service trunk, the portion of the system involved in a telephone connection will` lirst be @described and asA detailed description of the circuit 4connections and lapparatus involved in such connectlon is given in the patent above referred to a description ofoperation will suffice fora clear understanding by those skilled in theart to .which the invention pertains.

In establishing` a straight telephone connection the operation is as follows, reference being had to. Figs. 2ftjo'7.

nection liltsreceiver R from hook H which bridgesy his telephone across line wires 1 2,

The subscriber at station A desiring a con-- energizing relays R1 and by way of-B, 19, 20, R3, 21, R', 22,5521, 1, station A, 2,

1T`2,2,/23, ground to battery. Relay R vlocks and completes circuitof ground lamp L and 135, 4o, 742, to

relay R1 the former from B, 19, 27, L, 28, T52, ground to battery, the latter from B, 19, 29, R1, 30, '155,-to' ground. Lamp L lights, and relay R11-completes circuit of stepping magnet M to interrupter I for intermittent energization over the path, B, 19, M, 31 T51, 32, T21, 33, I to ground. Magnet M moves switch S step by .step until Wiper ws engages a contact s connected to relay R15 (Fig. of an-:idle primar selector trunk, whereupon relays R5 and 15, (Figs. 2 and 3) are energized by current through B, (Fig. 3), 34,35, 36, T13, 33, (38 Fig. 2), s, ws, 39,

gound.l Relay R5 opens circuit of magnet at T51, locks itself to ground through T52 and completes circuit of R11 over path B, 19, 41, R11, 42, T53 and ground.. Relay R13 locks itself to battery through T151, 43, T121, 44, and 34 to B; connects battery to one terminal of relay R12, through 3 4, 35,

T133, 4:5, 46, T152, 47, and 48; and also-com pletes circuit -of rotary relay R18 through T152 and interrupter I, so that this relay is energized intermittently, its circuit being: B,---`

34,35, T133, 45, 46, 4152, 47, 49, 5o, R18, 51, T121, 52, T152, Ito ground. vAt each actuation of relay Ris magnet M5 is energized by current from B, 34, 57,d contacts 58 of foot step switch S1, 59, M253, T181, ground, stepping primary selector switch S1 around until wiper w26 enga es row test contact a2 .whereupon relay 12 is energized over circuit B (Fig. 3), 34, 35,413,145, 46, T152, .47, 43,'.

49, @24, (Fig. 2) 2e, 741, ground to battery. lRelay R12 -locks itself to ground throng? T122, connects test Wiper f25 to sleeve relay 15 through 54, T125 and 55, and shifts interrupter I from rotary relay R18 to vertical relay R19 at T121, so that R10 is intermittently energized; over the circuit: B, A34,

T152, I, ground, to battery. At each actuation 'of relay R10 vertical magnet M0is energizedover the path B, 34, 60, M0, 61,.T101 to ground, stepping switch S1 up until wiper w25 engages individualtest contact c25 (Fig.

.' 2) whereuponsleeve relay R10 is energized .over vthe circuit: B', (Fig. 3) 34, 35. 62, R15,

55, T125, 54, w25, c25, (Fig. 2), 25, T12 (of relay R), ground to battery`; Relay R15 connects battery to trunk conductor 7, by Wayof T151, 63, 64, T111, 65, and resistance T, and at the Sametime o ens the circuitof relay R12 at T152. Relay 12 opens circuit of vertical relay R19 and magnet M0 is de-energized, which permits wiper w25 to stop on contact 2,025, wipers 'w5 'and w1 engaging contacts c2 and c1, respectively. Tiprelay R11is1now energized. through subscribers telephone in tor, by magnet M2 in circuit: B, 19, 41, 66,

67, 68, T01, 69, M2, 70, T111-, 71, I to ground. Switch S2 .continues to step around until wiper arm 403200 engages a contact s200 con-- nected to anl idle secondar selector, where-A upon relays R10 and R52, igs. 2 and 5) areV energized in series, theA circuit being: B, (Fig. 5), 86, springs 73-74 of operators s,'78, R52. 79, through Fig. 3 into Fig. 2, s200, 408200, 80, 81,.R10, 82, T112 to ground. The actuation of relay R10 causes the energization of'relay R0, the circuitbeing.: B, 19, 41, 66; 67,' T101, 83, 84, R9, 85, T115 to ground. Relay R0 locks itself to batterthrough T02, and opens circuit of magnet 2 at T01, -whereupon switch S2 comes to rest with wiper.

relay R2 as follows: B., to R2, 223, T0"1 to ground. Relay R8, grounds wire 80, shunting relay R1o out of series with relay R52 (Fig. 5), the circuit of the latter relay now going direct to ground by Way of wire 80 and armature T22. Relay R12 (Fig. 5) completes the circuit of rotary relay R39 through interrupter I so that said relay is intermittently energized byvcurrent over B, 86, 87, T501, 88, T211, 89, R50, 90, T521, I to ground. Relay R52 also connects one terminal of relay R to ground through 91 and T522, and locks itself to battery through 92,7225, 93, T202, 87, 86',`B. Each actuation of rela R50 energizes rotary magnet'M15 through 86, 94, M15,95, T501 to ground. Magnet, M13 steps switch S8 around until wiper 'w82 e11- gagcs contact 352. Thefirst rotary step of 'the switch S5 disconnects contacts 76 and 77 of switch F8 and, .connects contacts -76 and 290, which opens the initial energizing circuit of relay R22, (that relay, however, remaining energized through its locking circuit) and closes the circuit of oit-normal' lamp L7 as follows: B, 86,73, 74, 75, 76, 290, L7 to ground. When wiper 4022 engages contact 822 the rela R51 is energized over; the path': B, groun to T522 (of relay R12), 91, 96 R51, `97, w82, S82, 98, through Fig. 3 into Fig. 2, S20 (in switch S2), c0820, 99, T01, 68, 67, 66, 41, 19, battery. Relay R21 locks itself to battery through i100, T312, 101, 88, T501, 87 and 86, opens circuitY of relay R59 and closes circuit of', 'relay R10 at T511. Relay R20 opens circuit of magnet M13 at T501, which stops switch SB with wiper 1 thence through 291, 4, c, w1,

d T222 (relay R22),.91, R, 105, w81, 821, 45 (45 Fig. 3) T113,v 35, 34, battery.. Relay R20 opens locking circuit of relayR32 at T292, also opens circuit of relay R40 at T201, T101 of relay-Rm opens the circuit of "vertical magnet --M11 which stops-switch S8 .with wipers 'w32/w21.

w12, and w21, on contacts 32, 381,822, and 881. (Wi er w22 is raised oil row contacts by first step. Wiper 'w22 'en aging contact 812, (Fig. 5) relays R11' and- 2, (Figs. 5 and 3) are'energized through: B, (Fig'.v3), 34, 35,

3c, 5111, c3, 106,311, 107, ,(107 Fig.' 5), '8111 7 w11, 10c, 71111, 109, T111, 111,112, R11, 11a, T131, 114, .71111, 115, T111, 116,411, ground. 1 Relay R42, when actuated, opens series cirT cuitof relays Rl5 and R12." (Figs. 2 and 3) yat T121. Relay R1s disconnects interrupter'I at T122 andf relay R-(Fig. 2) opens circuitof relayI R11" at T12. Relay R11 -deenerg'izing opens'circuitsv of magnet.v M2, 'relay R9 and `.-relay'-"`R1, While relay .R2, its Cir# .cuit-,opened at T22, opens circuit of stepping magnet M at T21. This prepares distributing switches S and S2, with their relays', for another call. Relay R11 becom-l ing energized closes circuit off night alarm N through: B, se, 110, 117, 118, T111, 119, N, to ground; closes circuit of ard lamp L2V (Fig-16) through B (Fig. 5 86, 110, 117, 11s, r1, 120, 121 (121 Fig. e), L2 to ground; closes circuits oi service meter E (Fig. 5)- throu h B, armature T312, 122, 242, and magnet o servicemeter E to ground; and line lamp L (Fig. 6) through B (Fig. 5), T212, 122, 123, (123 Fig. 6), Ls to ground. The operator, perceiving the signal, depresses listeningRkey LK (Fi 6) energizing listening relay 2 (Fig. '5) t roughzB, (Fi 5) 86, 87, T111, .88, 101, 5112, 124, R11, 125, 125 Fig. 6), contacts of key LK', 126 to ground. Re# lay R"s energizing, opens series circuit of relays R and R2 at T111 and vlocks itself to groundthrough T211, and 114,1as previously traced. lRelay R12 deenergizing, opens circuit of relay R11 at T421. -Relay R"s completes the operators listening circuitas follows: receiver OR, 127, tip p, ls ring 128, T2", 129, 131, w, 32, 130 (130 ig. 3 I, T111, 9', T22, 7, condenser C', 5, ws, c2,\(Fig. 2), 3, T21 over subscribers line andback to T22, (Flg' .3), 6a condenser (12,8, IT122, 10, 134, T12, 135,' (135 Fig. 5), .911, "10252132, 136, T132, 137,' coil 10,', 138, jack spring 1j', plug sleeve p', 139, re

ceiver OR.

Should the calling subscriber hang up receiver before the operator is connected, tip relay R14v (Fig. 3) is deenergized, its circuit being open at the subscribers switch hook contact, and -sleeve relay R15 remaining energized in series with cut-oil' relay R2 (Fi 2), energizing circuit of relay R12 (Fig. 5 is completed as follows: B, (Fig. 3) 34, 36, T151, 63, T111, through resistance T, 'trunk con- 11151011 7, 5122, 9, T111, 130 (130 Fig. 5), 81, w29, 131, l129, T232,128, 154, R28 to ground. Relay R88 energizing, connects operatorls tonertest circuitfllt through155 and 137 to operators receiver, and the operator loeing thus notified that the calling `subscriber has disconnected, actuates the release and trunk start"key RK, (Fig. 6) whereupon relay R" (Fi'g. 5) receives current through: B, 86, 110, 156, R", 157, (157 Fig. 6) key RK to ground. R87 then energizes starting relay Rsin sc .ries with relay R12, (Fig. 3), through: B, (Fig.l 3), 34, 36,- r111, 63, 100,1112, 107,; (107 Fig. 5), 8111, w11, 108,521, 109, 5111, 111, 141, R22, 140,158, T271, 159, 157 to ground through Rlf Relay R42 energizes relayR41 which througharmatures T111 and T412 connects iin-- -pulse sending vwires 130 and-135 to tip and sleeve conductors 9 and 10 respectivel The circuit of relay R11 is: B, 34,44, T121, 21, 143 contacts -144 and 145 of foot-step switch F to ground.. Relay RF being energized, opensl the locking circuit of listening relay R28 at T221 and locks itself through T321, 115, T252, 116, T222, toground; and also establishes a locking circuit for relay R7 through 159, T271. 158, 140, T221 to ground over the same path traced for locking circuit of relay R. Armature T262 closes circuit of guard lamp .L2 (Fig. 6) through: B, (Fig. 5) 86, 110, 117, T892, 150, 121, L2 to ground, and armature .T322 partially closes circuit magnet M1 so that when cam disk D11 (Fig. 6) closes contacts 0311, said magnet-is momentarily energized, stepping switch Ss forward'one step. The circuit of magnet M1 is: B. Fig. 5), A86,-110, 117, M1, 153, T212., 152, T261, starting wire 151, (151 Fig. 6), contacts $11, to ground.

Immediately after switch arm ws engages contact 112,111 vnumber of ground impulses come from the sending machine over wire 173 (as hereinafter described) by way of contact 111, .wiperarm ws, trunk-conductor v131, 1511 r11, 130, Fig. 3),r111, relay R11 to battery rand ground. Each actuation of relay R211closes circuit *of magnet M2 atn() selector switches S* and S", through 106, 177,

T112, 178,v 179, M and M" in multiple, to B. These magnets restore their respective switches to normal position. The circuit of sleeve relay R1 is now open at auf, and itssprings' 1 5 and-1760i switch F5 being armature T131, opens the series circuit of relays R12, and R33 (Figs. 3 and 5). Relay R33 opens at T331 the locking circuit of relay R33.

s wiper arm 708331 is resting on contact ,13333 and armature T332 of relay R36 is retracted, the retraction of armaturel T372, of relay R37, closes circuit of relay R33 as follows; B, se, 110, 117,11, 16s, 161,13, 29e, 113, 10.93, 164, R33 to ground. Armature T332 of relay R33 connects one terminal of stepping magnet M13 to interrupter I for intermittent energization over the path: B 86, 110, 117, Ma, 153, 1353,1 aground. agnet M13 steps around switch arms w83, w83 and 'w83-0 over their respective'bank contacts. After wiper 4arm wa33leaves contact 233"0 and sweeps over contacts 31330 m1511303 relay R33 is kept energized through B, 86, 110, 117, T332, 163, 162, contacts 33330 to 53333 and so on as reviously ltraced. When wiper c0833 reac es contact 63303 the circuit of relay R33 is -aglain changed 'and-said relay is energizedv .w ile 'the arm sweeps over contacts 633 to' 95800, through: B, 86, 110, 16e, es@ to 913.

@0830.12164, and so o n as 'previously traced: When wiper arm c0830- passes ofi the last contact 93331itopens the circuit 0 1 relay R33, which disconnects magnet M133from interrupter'I at T333 and stops'switch S3 4with its wiper arms w83, ws3`and '103333 clear .ofall contacts. Shortly. before switch S3 `comes to normal position, contact springs'16`8i are momentarily closed kby a cam on the switch pindle and'release inagnet'M13 is energized rough: B, 86, 169, 170, M13,17 2, 168,

ground. Magnet M13`restores swltch to normal position, ready for another'call.

If the calling subscriber remains on the' line, theo erator, on ascertaining the num,- berwante l sets up the same on her key (Fig. 6) 'by depressing the key in strip strip K2 4corresponding:to the second digit, that in'the third lstrip-K3 corresponding to the third digit, and that in the strip K'1 co1'- responding to .the particular ringing generator tov be selected, and then actuates startcut-o relay R42 (Fig`. 3) through:

Fig. 3), R12, 106, 63, 1331,34, battery to ground.. Relay R12 opens trunk conductors 9-v-7 and 10-8 at T122 and T323, and energizes relay R11 through: B, 34, 44 4, T121, R11, 143, contacts -144 and 145 of switch F3 to ground.

Armatures T111 and Tfn-connect the impulse wires"130an d 135 to rotary and vertical relaysR21 and R23, res actively, while armature T113'connects con uctor 147 Ato one terminal'of relay 11u-through contact 146. Starting relay `R311-- (FigA 5)v takes ground ofi relay R33 through 114, at T331, and,` locks itself through T331 and115 to ground Vas previously set" K2. corrs'pondlng to I'the'.,irst digit, that in the l traced. Armature T332 maintains the circuit ofthe guard lamp through B, 86, 110, 117, T332,,15O, A121, guard lamp to ground, as previously traced.v Armature T333 connects starting wire 151l to stepping magnet M13 and partially completes a connection from B, (Fig.- 5)136,A 110, 117, M15, 15s, T358, 152, T333, starting wire 151 (lm-Fig. 6) contact springs e111, to ground; so that when cam disk D11 (Fig. 6) closes contacts d, said ymagnet is momentarily energized, stepping switch S3 forwardv one step. Immediately after cam D11 (Fig. 6) has passed under the contacts du, the number cams D to D10 inclusive, pass under their respective contact springs d to d1 inclusive, the cam D maintaining the closure of contact d during one .closureof the interrupter contact springs d', vthe .cam D2 maintaining the closure of its contact springs i2 during two closures of -saidl interrupted contacts, and so on to the cam D10, which maintains the 4closure of its contact springs Z111 during ten closures of the interrupted contact springs. During the passage ofthe number 'cams under their-contactsspri'ngs, ground impulses (corresponding in number to the first. digitof the wanted line) are sent over the hundreds impulse wire 173 to the rotar Arelay R21 of the irst #selector switch S3, igei). Assuming for example, 'that the num relay R21 will be momentarily energized two times, through: ground,d, 190, d2, 191, 192, 193, k12 ofstrip K', v173, 173 Fig-5), 133, @083131, w80, `88, 130 (130 Y1171.3), T111, R21, battery Bv to ground. Relay R21 intermittently energizes magnet M3 which steps switch' S3v to 'the second row of contacts through lwhich the connector containing wanted [subscribers line is accessible. At the first -rotarystep of switch S3, contact springs'l75-176 are closed, completing the circuit of ofit'fnormal 4lamp L3 through B, 103,104,L3, 105,106,- 1.7 6,175, to ground; also partiallypclosing' the release circuit through magnets M3 and M1, Ahereinafter described. 'Afterthe'numbercams have passed under their respective springs `cam D11 again -closes its contacts Z11 stepping switch S3 around to 'bring itsl wipers into engagement withjthe next set of contacts. Wiper'arms w33, w83 and 'm33o of switch S3 now engage their respective contacts 233', 213, and 23303, and' cam D12' (Fig.v 6) connects test impulse ,wire 189 through springs (i12, conductor 190 and springsd toground during ten closures of springs d?, whereupon "vertical relay R20 (Fig.` 3) is intermittently energized through: ground, d1, v190, du, 1 89 '(189 Fi 5), 2330, ,'ws30, 132, w31, .93.1, 135, (135 Fig. 3 T112, 199, R2, 196, battery, to ground. Relay R23 1ntermittently .closes circuit of magnet M7 at T291, stepping up wipers @93,1013 and w1" of .the first selector switch `S3 to en age contacts 013, c, and 023, respectively,- eading to a r wanted is 246-3,'

circuit of relay R41 is opened at Contact4 w21, S21, `135, (135 Fig..l3), W12-134, 10,'fw1,

s rings 144 and 145 of switch F, and should c1?, (F1g;.4), 15, 11222, 228,v R22, 229, 230, 1-221,

t e'connector trunk (Fig. 4) be busy because 233, 712111, 231, battery to ground. Each actuof the wipers of another first 'selector switch 'ationjof VR22 energizes magnet.. M9- thrcughzg resting on the multiples of contacts q2, re- B, 208, 237, 239, .M,'240,.1-221, ground. Magconnector trunk(Fig. 4). At the first verti- 'tacts d1, (Fig. 6) 190, d?, 225, 226,227 14:24 of cal movement of the spindle of switch S the strip K2, 224, 4.(224 Fig. 5), 422, .fws1,.132,

l(al -R1 would remaln energized through B net -M moves switch S forward four .steps 1 g' 3) 34a 44, 7142-1, R, 146, 7'* 13, .147, wma bringing .Wipers w11. and w12 onto the fourth c2 (Fig. 4) 4to the. multiples of o2 and row of contacts, in. which lie the wanted'line Y thence through Ythe circuit of the other first contacts.

selector by way of its wiper w11?. (as in Fig.

tical relay R2 stepplng the wipers up tothe' to M1 and lights lamp next set of contacts, and-so on until an idle through: B, 210, 246, 264, 7222, Li1 to ground.

connector is reached, when, relay'R41 being Cam D11 (Fig. 6) again closes contacts 11 deprived of groundureleases. its armatures. and sends one. impulse over wire 151, .actu- The4 armature T112, disconnects impulse wlreQ ating switch S3 to step its wipers onto`their 135 from the relay R2, stopping switch S2 with its wipers (w11, w10, and w147 on contacts 013, 01, and c2, respectively, of the connector trunk (Fig. 4). .The impulse Wires 130 and`135 are now connected to ythe tip and sleeve conductors9 and 10 through armatures 02111, 'and 1212 respectively, and contact c2 (Fig. 4) and its multiples are connected to ground*through-:pto147 (Fig. 3;, 147,- and T112. After cam D12 (Fi 6) las passed springs` (i12, starting cam gD, again closes springs du, steps switch S3 around to bring its wipers ingo engagement with the third set of contacts. .Wiper arms we, 42.92, and ws2 now engagevtheir respective thirdcontacts. The number cams now pass under .their resective'contact springs orthe third time an send impulses, corresponding in number to the desired ringing generator-(in this case No. 3)-, to relay 'R22 (Fig. 4), through: ground, springs di (Fi 6), 190, cl2, 198, 203, k12, 197 (197 Fig. 5 322, wss,

'131, w8", 88" 130, (1.30 Fg- 3), T2, 9, w", C, (Fi 4) 1e, 1261, 204, R23, 205,- B to ground.-

Eac actuation of relay R23 energize's magnet M11 of switch S2, through: B., 2.08, 209, 210, and 211, 212, 213, M11, 214, 215, T221 to ground. Magnet M11 moves switch S7 for# ward three steps, bringing wipers we", 'ws 1, and ws1 onto contacts 3, 321 and 31.11 Irespectively'. v

The first actuation of R22energizes R24 and 1R21, the irstthrough: B, 207, 205, 22.2, 247,

R21, 202, 200, 02, w1", (Fig. 3) 147, 1212 to ground, lookin itselfto .battery through 1211,'250, 1222, 20 the second .relay through: 14222 (of relay R22)234, 230, R27, 235,122, 236, 202, to ground, locking itself to battery through: 232, T211, 233, T221, 231. Cam'.D11 (Fig.' 6), again closing contacts 11' moves switch S1* one step .bringing its wipers onto the Jfourth `set of contacts. Wiper 20.92- now engages contact 423 and the number cams #close their respective springs and send impulses to R22 (Fig.l4)-through: ground, confifth set of `contacts. After cam D11 has passed contacts du, the number cams again A The rst lactuation of R22 .opens the lock- 3), 147,1'112 ground, to battery. The armaing circuit of R21 atr222.-v The first rotary ture fm 0 relay. R21., remaining attracted stepopens springs 210-211-and closes;.210 permits the next test impulse to energize ver. 246, which shifts battery. lead 209 from M11 L by current.

actuate ther respective s ring contacts-sending unit impulses throug 241,' (241 Fig. 5), 522, wsa, 131 to R22 (Fior. 4). Each actuation of relay R22.ene1'gizes TM, through: B, 208,

20.9, 210,246,244,1\i1,243 71272, 215,421, to l ground.- Magnet M1 is actuated six times, stepping wipers w12 and w12 onto contacts c1" and 01r (Figs. 4 and 7 respectively). The first actuation of relayR23 again energizes R24 through 72232* and R22 locks itself. and opens the circuit through relays R21 and R22 to Wipers w17 and w18, at 42242. and T221 to prevent aiecting said relays while the wipers are passing over other line multiples. After the number' cams pass their springs, and before cam D11 closes itssprings, cam D13 closes spring 12, sending a single-testimv vpulse through 292,- (292 Fig. 5), 52,.110.91m,y

132, to R22 (Fio. 4), whereupon if the want- .l

) is busy, with wipers w12,

ed line (Fig. .11212, of another connector switch, or lw11, w* of a primary selector switch, resting onmultiples otcont'acts c", C12, the test relay R22 (Fig. 4), is energized, in the first case through: ground, ,M1-12 (Fig. 3), 147 w12", 022

(Fig. 4), 200, 201, R20, 251, T223, 252, 4281., 2.53,'

18, w12, 012, (Fig. 7) to the multiple of 012. on which the other connector switch wipers are resting, thence through thatonnecton by way of 401218,25a4281, 252, T223, 259,11, T211, 250, 1'222, 207,113, to ground, in the second case: R22, 012, thence throughthe multiple otl 012, on which wiper w, of a primary selector is resting 29.4, 11122, 55, R12, 3 4, B, to round. Relay R22 when energized locks itsel to battery thrugh 262, r21,'connects the busyl back Bz to trunk conductor 16, through 71222l and closes the release circuit of S" through: B, 208, 209, 21o, 246, 264, 265, 4223, 267, 269, M12 to ground'. M12 then releases the connector switch S1?. After this impulse relay R22 is deenergized, and ncompletes the-restoring circult of switch S1, through: B, T222, 250, T211,

its circuit is opened between 606700 and .2700.- The test relay R remains locked, holding busy-back B2 on trunk conductor 16,--to

signal the calling subscriber, (Fig. 2), who then hangs up his receiver, opening circuit of R14 (Fig. 3)- which deenergizes and releases magnets M3 and M2 of switches S4 and S5 through ground, 175, 176, 106, 177121'42,l 178, 179, M3 and M2, (in multiple), B, to ground. Thel switch. S5 inrestoring opens the circuit of R22 (Fig. 4) at 0200 and w147 (Fig. 3) and the busy-back is disconnected. J Ifthe wanted subscriber is not my, R27 remains locked, and aftervthe test impulse R22 deenergizes, which energizes R20 (Fig. 4) and R43 (Fig. 7) in series, through: B, (Fig.

4), 1222, 250,l T221, R26, 259,1-222, 252, 72221, 253,

18,2018, 020, (Fig. 7) 255, R23 to ground. Relay R20 closes trunk conductors 15-17 and 16-18 'at 1'202 and 261, respectively, whilel R23 (Fig. 7) connects line terminals 256 and 2571130 extensions y254 and 255. Simulta-v neously with the energization of R20 and R23, ringing relay R28 is connected through: B, 222, 25o,I 5221, T222, 277, 5222, 278, R22, interrupter I2 to ground. ,Y l

lImmediately after the test impulse cam D12 (Fig. 6) causes contacts du to send an impulse over.wire 151, stepping switch S0 (Fig. 5.) Vforward one step bringing its wipers onto the sixth contact set.' When 203300 engages'contact 60200, the restoring relay R2l is 'energized fthroughr'B, 86, 110, 166, 6s300 to 92200, 164, R22, to ground.. Re-

lay R02 opens ,circuit Aof R02 andfR,

(Figs. 5 and .3 respectively) at 92302 vand 92.202, 'while ,r00s *connects magnet vM10 l for intermittent-energization throughr B, 86,2110, 117, M12, 155, 5252, I to Magnet M10 steps switch S0 forward, holdground.

ing R20 energized through 2108000 and con;

tacts 6300 to 92000, untily the wipers have reached normal position, as shown.'- The secondary selector switch S0 is restored by the cam on the switch S0, inpassing, and the operators circuit ,is ready to receive anothercall. '-2

'Ringing relay R20 is intermittently energized by interrupter I2v to :ring subscriber lA0, (Fig. 7) through .circuiti G0, 279, 3270,

@5820, 28o,- 5222, 17, w11, 012, (Fig. 7) 254, 1221, 256, 282, ringer Q2, C20, 285, 257,'1222-258; 255, cls, w10, (Fig. 4) 18, 253, T282, resistance 72', 285, 208, 206, B to'ground, and generator G2. At each energization of relay R20 the circuit of lamp L0 is opened at 1200. When the called subscriber A0 takes down his receiver, he bridges his telephone across the' line, and at the next non-ringing interval the circuit of the tip relay R20 is closed through: B, (Fig. 4) through R20 to 018 R25 opens circuit of R22 at 12252, relay R27' opens circuit of ringing relay R2Bv at 12272, and the ringing ceases.

The calling, and called Asubscribers A and A2, respectively, arel now connected for conversation over the circuit indicated in heavy lines in Figs.` 2, l3, 4 and 7.

Relay R2 connects test. contact e200 through: 0200, 200, 202,236, 122-52, to ground side of battery, whichI renders vthe trunk busy in case the calling party should hang up first. At the end of the conversation, 1when .calling subscriber A hangs -up his receiver the circuit of the tip relay RM (Fig. 3) is opened, whereupon armature 12142 falling back, closes the circuit of release. magnets M3 and M2 ofthe switches S* and S5. which return to their Vnormal position. When called subscriber A0 hangs up his re- `ceiver, the circuit of tip relay R20 (Fig. 4)

207, 289,708?, 290, 269, M12, ground, to bat-v tery. The connector switch S0 then returns to its normal position. l

In the establishment of a connection for furnishing broadcast service, theoperation "and the apparatus employed is the same except that the connection is made through the line `tube .connector trunk or link circuit, Fig. 8, to one ofthe program busses or trunks,. thev subscriber calling from his broadcast receiving set or from an extension telephone set vand receiving the program on the loud speaker receiver of this set.

The subscriber-s broadcast receiver set (Fig. 2) comprises a loud-speaker receiver 307 connected to the secondaryl winding of a transformer 308 whose primary winding is connected with the .line extensions or branch wires 309--310 in series with a transmitter 311' and switch H2, the line extensions 309-310 being extensions of the line conductors 1-2, respectively. Thus the broadcast receiving set is'connected as an extenvsion telephone set.

The line tube connector-trunk and switch of- Fig. 8 is similar to the connector trunk and switchof Fig. 4butA much more simple as the ringing, testing and busy-back signaling circuits and apparatus are omitted. Here the tip and sleeve trunk circuits are extended from the contacts e0-01,0, multipled in the banks of selector switches suchv as that of Fig. 3, to the wipers w20--wf0 through the contacts of adisconnect-relay R02, and coupling, transformer 315 to line tube 316.

The relay R*s2 is arranged tovopen the trlmk circuit between the transformer and the bank contacts when energized to normally maintain connection of the rotary and vertical repeating relays lim-R51 to the tip and sleeve conductors 301-302 respectively. The repeatlelays control the -movements of the switch through the rotary and vertical driving or stepping magnets MzL-Mzl` in a manner similar to that described in connection with Fig.'4, the rotary magnet Mz being also controlled through vertical footstep switch 313 operable upon the firstA vertical movement ofthe connector switch S11. The magnet M 22 is the release magnet for the switch S and is controlled jointly by a starting and holding relay R5* anda Yr0- tary foot-step switch 314 operable upon the,

first rotary movement of the switch. The relay R5* also controls the initial energizing circuit of the relay Rz through the vertical foot-step switch 313, the relay R52 having a locking circuit controlled through a normally closed contact of the rotary relay R. Relays R52- "4 jointly control the relay 53 for controlling the energization of the filament circuit ofthe line tube 316. Various' detailed circuit connections and functions of the different relays and switches will be made clear in the description of operation which will follow later. .Connector switch S11 is provided with a contact bank similar to that ofthe connector switch of Fig. 4, but instead of the contacts such as M -04 fcrming the terminals of subscribers lines theyform multiple connections to program busses and trunks 317, 318, 319, 320. The program. busses such as 317--318 are supplied with matter to be distributed broadcast to the subscribersfrom a suitable source of supply,` not`sh0wn, but which may be the audio output circuit of a radio receiving set or other program supply4 means such as those shown and described in my copending application Serial No. 10,916 filed February 21, 192

The program trunks such as 319 and 320 constitute trunk lines leading to other central stations 'for the purpose of receiving broadcast matter available at such other sta.- tions. These program busses and trunks are multipled in the banks of the broadcast service connector switches S11 and are assigned to a given group or groups prefer.-

ably the 10th hundreds group as here shownf by way of example. The output terminals of the trunks of these connector switches therefore appear in the last or tenth vertical rows of the contact banks of the selector switches S5. All calls for numbers beginning` with 10 (or zero on the operators key set) such as 10-46 will be made through a broadcast service trunk and connector switch S with a line tube 116 included in the connection. Thus the operation in establishing a connection for broadcast service is the same as that for a straight telephone connection as described except that the connection is made through aconnector switch S11 with the busyv test and ringing omitted. Theoperation of the system in the connection of'a subscriber for broadcast service -is as follows: The subscriber at, substation A (Fig. 2) desiring broadcast service, closes the switch H2 at his broadcast receiver ex-l tension set thus closing the line circuit by. wa of 309, primary of transformer 308,Y lswltch H2 and `extension 310. Thisclosure of the .line actuates the subscribers line v terminal apparatus at the central oice in the same manner as that caused by closure ofl the line through his switchhook contact H and as previously described in detail, for the establishment of telephone connection, and as previously described, connects the calling subscriber with an idle, operators' l key set. The subscriber now gives the program number wanted, for example 10-46, which indicates that connection 42 in the 10thI or broadcast service group is Wanted. The operator thereupon depresses the 10th key or the key marked 0 inthe hundredths .row of .her key set, which key in the drawmg (-Flg. 6) is connected'at k1 in row K1 also key k2* in rowK, key 7c3 in row K3,

and startin key SK in row K4. This results in di erent groups of impulses being sent throu h the operators circuit of and'over t e conductors 130-135 of Fig. 3 all in a manner similar t0 that set out in the description of operation for the establishment of a telephone connection. In thev present example lthe order of impulses will run as follows: first, 10 impulses over con ductor 130; second, 10 test impulses over conductor 135; third, 4 impulses over conductor 135; fourth, 6 impulses `over con# ductor 130, and fifth, a single test impulse, now used as a shifting impulse, over the ,conductor 135. The first set of 10impuls'es over the conductor 130 followed by the the test impulses over conductor 135 will cause the' Flg. 5

selector switchv S to bel irst stepped around to the 10th row of contacts and then stepped up to select an idle connector'trunk circuit and switch S11 (Fig. 8) permitting the relay R9 (Fig. 3)'-to become deenergized and extend the connections of conductors 130--135 through wipers 'mL-wl and contacts @-01.0 to conductors 301-302, all inthe manner similar to that previously described. Immediately the armatureir"18 yof relay R (Fig. 3) falls back grounding-'the wiperv w1", a circuit is completed from this ground connection through wiper com, contact c1" (Fig.'8) back to ground, the completion of' which ycircuit. energizes relay R54. Relay R attracting its armatures completes the enerrelay R through'battery B and l gizing circuit of disconnect relay R52 from attery B through R52, conductor 323, contact 325, 1511 to ground and back to battery B. Attraction of armature 1522 removes the battery connection from release magnet M22 .and partially completes ,the circuit of relay R52. Energization of relay R52 Adisconnects the trunk conductors 301-302 from 303- 304 and connects them to conductors 327- 328, removes the ground` connection from filament relay R53 at 1'522 and completes a locking or holding circuit for itself through 1'525 and armature 1502 of relay R50.

v'321, 322, armature 1^51, rotary magnet M20,

contact 324 of vertical foot-step switch 313 to ground and back to battery B. The energizations of magnet M20 causes the wipers of the switch S11 to be stepped around to the fourth row of contacts, the first step in this rotary. motion causing the rotary footstep switch 314 to close its contacts.

The fourth set of impulses, six in number, coming over conductor 130 (Fig. 3), pass i through conductor 133, wiper wg', (into Fig.

- 8), contact c, 302, 1'521, 328, vertical rela R21, 326, rotary foot-Steg switch 314 throug battery B to ground. ach energization of the vertical relay R51 energizesthe vertical magnet Main a circuit which may be traced from .battery B through circuit elements, 321, 11511,4 M21 to ground and back to battery I, B. This causes the switch S11 to step the .ductor 135 (Fig. 3)

wipers lm2o-w40 up to the sixth pair of contacts such as 02U-01 forming multiple' connections to the desired program trunk, the. first vertical movement of the switch-operating the vertical foot-step switch to open its* contacts-324 and 325.

The single test impulse coming over oonpases throughl cir cuit elements 134 (into Fig. 8) 01, 301, 327, rotary relay R50, 321, battery B The single momentary'energi'zation of the rotary relay o ens the locking circuit of disconnect relay 52 which latter relay deenergizing connects the trunk conductor 301-4 302 through to 303--304 and to the terminals of the secondary winding of transformer 315, and completes the energizing circuit of filament relay R52' through circuit elements B, 1'52, R22, 1'522 to ground and back to battelg B.

nergization of R52 completes the energizing or filament circuit of the line tube 306 thus extending the connection of trunk to ground.

316, wipers 'm2o-'w10 and contacts 620--01-2 to the desired program bus 317. After this test impulse the operators key set and circuits associated therewith `become disconnected as before described leaving the calling subscriber A (Fig. 2) connected through Figs. 3 and 8 to the program bus 317 (Fig. 8) over the circuit indicated in heavy lines.

When the subscriber at-substation A. vopens the switch H2 at the broadcast receiving set, the linev is opened and the switches S2 and S5 are released in the samemanneras that previously described as resulting from the openirlig of the line at the telephone switchhook after a telephone connection. When they switch S5, in releasing, disengages its wiper w1 from contact 0122 (Fig. 8) the holding relay R51 is deprivedV ot its ground connection through conductor 326, contact C121, wiper w117 (Fig. 3) and armature 1212. The retraction of' armature 1522 of holding relay R54 opens the circuit of filament relay 52 to deenergize the filament of line tube 316, and closes the circuitof the release magnet M22 through circuit elements B, 1512, M22, 314'to ground, Energization ot release magnet M22 causes the swltch S11 to release and returnv to the normal position indicated first closing the contacts of vertical foot-step switch 313 and lastly actuating the rotary toot-step switch 314 to openl its contacts which deenergizes the release magnet, restoring all the circuits to the normal condition shown.

While I have here shownv a. simple lino tube 316 connected as a stage'of audio am pliication, it is to be understood that this simple showing is by way of example forthe purpose of disclosure only and that the invention is not limited thereto but contemplates the use ofa set of several tubes in place of the single tube shown which set may constitute' an ampli ing set for either audio frequencies, radio requencies or both, or may constitute a complete receiving set adapted to receive directly on the carrier wave freuency.

What claim is: Y

1. In a system of broadcast distribution, a central station, subscribers stations and wire lines interconnecting them, a source of electrically transmitted broadcast signalin currents at the central station, a plurality o' one-way amplifying units for said signaling currents, mechanically actuated switching links at the .central station, circuit connections from said switching links to said amplifiers, said subscribers lines and said source, respectively, there being one amplifier unit er line only, and means to close said circults when a switching operation is complete, so that the corresponding unit is automatically brought into operative condition, in such relation to its line as to amplify in 1the direction of said line when calling, on y.

2. In a` combined telephone exchange and broadcast distribution system, a central station, subscribers stations and wire lines interconnecting them, a source of electrically transmitted broadcast matter at the central station, a line audion tube, automatic switching means having a busy testrelease circuit and a-rrangedfor interconnecting said subscribers lines, and. automatic switching meanslwithout a busy test release circuit for connecting the output circuit of said tube with any one of said lines individually andl the input circuit to said source.

3. In a system ofbroadcast distribution, a central station, subscribers stations and wire lines interconnecting them, a source of electrically transmitted broadcast signaling currents at the central station, one-way amplitying audion tubes at the central stat-ion, and automatic switching means for selectively connecting thefoutput circuit of one of said tubes with one of said lines individually and means for connecting the input circuits of all of said tubes when so selected with said source in common. Y

4.-. In a system of radio broadcast distribution, a telephone central station with subscribers9 substations and wire lines connecting them with the central station, a plurality of radio receiving sets at the central station, a plurality of individually available one-way audion tube amplifying sets at the central station and automatic switching means, with circuit connections therefrom to one or more of said lines, to one of said amplifying sets, and to said radio receiving sets, and means controlled by a calling subscriber to actuate said switching means to close said circuits and thereby to connect his line through one of said amplifying sets to one of said radio receiving sets, to amplify in the direction of the calling line only.

5. In4 a system of radio broadcast distribution, a telephone central station with subscribers substations and wire lines connecting them with the central station. apluralityl of radio receiving sets at the central station, link circuits terminating in automatic connector switches, automatic switching means for connecting a subscribers line to any of said link circuits, some of said link circuits containing audion tubes operatively connected therein, and multiple line terminals for said subscribers lines, the connector switches of the links not containing audion tubes being provided with the usual busy test circuit and having access to said multiple line terminals only, and the `connector switches of the links containing audion tubes being without a busy testcircuit and having access to said radio receivlng sets only.

6. In a system of radio broadcast distribution, a `telephone central station with subscribers substations and wire lines connecting them with the central station, a plurality of radio receiving sets at the-central station, link' circuits terminating in automatic connector switches, automatic. switching means for connecting a subscribers line to anyof said link circuits, ,some of said link circuits containing audion tubes opera ively connected'therein, means 'for transmitt'ng a test impulse 'to eachlink circuit and .multiple line terminals for said subscribers lines, the connector switches of the links not containing' audion tubes having access to said multiple line terminals only, and lprovided with means responsive to said test impulse to test the' condition of a line, and the connector switches of the links containing audion tubes having access to said radio receiving sets only, and each provided with means responsive to said test impulse to energize the associated tube. l

7. `In a system of one-way radio broadcast distribution, `a telephone central station with subscribers substations and wire lines connecting them with the central station, automatic switching means at the central oiiice comprising link circuits terminating in connector switches, different switches having access to diii'erent groups o subscribers and of broadcasting terminals, those switches having access to said broadcasting terminals having audion amplifying tubes in their associated link circuits arranged to transmit and amplify in theI direction of the calling subscriber only.

8. In a system of one-way radio broadcast' distribution, a telephone 'exchange 'system having a central station with subscribers substations connected therewith by wire lines and mechanically operating switching means at the central station for interconnecting the subscribers wire lines, radio broadcast receiving means at the central station, having its output circuit arranged to be connected with any desired number of subscribers lines in parallel through said automatic switching means without sa'id output terminals testing busy to any subscriber, and means operable only in the connection lof a subscribersline with the said broadcasting output circuit to include an audion tube in said circuit arranged to transmit andl amplilfy in the direction of the subscribers line on y.

. 9. In a system of radio broadcast distribution, a central 'station with subscribers substations connected therewith through wired lines, a radio relay set at the central station, one way amplifying sets at the central station less than thenumber of lines, and automatic switching means for interchangeably connecting 4said one way amplifying sets between said subscribers lines and said relay set to take' from said relayset in common and transmit the signals over the subscribers lines individually.

10.1In a system. of broadcast distribution, a central station) subscribersrstations and wire lines interconnecting' them, a source of electrically .transmitted broadcast signaling currents atvthe central station, amplifying audion tubes at the centralv station, .automatic switching means for selectively connecting the output terminals Aof said tubes with said lines separately and individually and the input terminals of said tubes, with said source of broadcast signalingA currentsy in common, and busy test means associated with said amplifying tubes operablevto prevent the connection of more than one line .with the same audion tube;

11. as'ystem of broadcast distribution,

a central station, subscribers stations and -wire lines leading therefrom tothecentral station and terminating thereat in line terminals, a source jof electrically transmitted broadcast matter having distributing terminals g at `the central station, switching means for connecting any one of" said line terminals Withany other of said line terminals or said distributing terminals, amplifying means, and means operable to exclude said amplifying means in the connection of a line terminal with a line terminal and to include said amplifying means in the connection vof aline terminal with said distrib- .uting terminals.

In testimony whereof I hereunto affix' my signature.

. EDWARD E. CLEMENT. 

